The present invention relates to a device for a bookbinding machine for applying and pressing on a cover.
In adhesive binding an inner book (comprising a multiplicity of printed sheets cut and glued along the back and continuously advanced in a conveyor system), is joined to a cover which was previously separated from a stack, then scored and fed in an aligned manner to the inner book. The cover is pressed in the so-called press-applicator against the back of the inner book and the side faces adjacent thereto by means of synchronously moving pressing bars during the continuous movement of the inner book.
Known, for example, from U.S. Pat. No. 4,153,963 is an arrangement in which the back pressing plate is moved cyclically in a horizontal reciprocating manner by means of a crank mechanism having two cranks arranged parallel to one another, while the pivots of the cranks are moved up and down by controlled movements of eccentrics. The side pressing bars are guided horizontally in bearings, transversely to the horizontal reciprocating motion, in a support plate of the back pressing plate, and are moved towards and away from the inner book by connecting rods having fixed pivots in a parallel crank arrangement during the horizontal reciprocating motion, the opening width as the distance between the side pressing bars being very large in their outer reversal positions. For adaptation to inner books of different thicknesses, one of the two side pressing bars has a telescopically adjustable configuration and its connecting rods are resiliently coupled to the frame.
DE 33 40 859 C2 describes an arrangement having a movable carriage supporting the back pressing plate, which carriage is horizontally movable in a guide sledge which executes a vertical movement, the movement of the side pressing bars towards the inner book during the horizontal motion of the movable carriage being executable by means of laterally arranged guide tracks together with guide rollers associated with the side pressing bars. The opening width of the side pressing bars in their outer reversal position is optimally defined, so that during processing of reinforcing strips said strips do not pass between the side pressing bars and are then crumpled, and so that the guide and support rails of the cover feed mechanism can be positioned close to the inner book for the processing of narrow covers. By displacing the guide tracks along the inner-book feed direction the opening width during the upward movement of the back pressing plate is adjustable. When pressing on a reinforcing strip, unlike the cover, the side pressing bars must be positioned close to the inner book so that the reinforcing strip is drawn tightly around the inner book.
This adjustment, however, can be made only at a standstill and requires a long phase in which the horizontal movement of the back pressing plate matches that of the inner book conveyor. Furthermore, the timing of the pressing by the side pressing bars is displaced relatively to the vertical movement of the back pressing plate. In the last-mentioned arrangement the actuating devices for the side pressing bars are arranged on the moving system. The maximum cycling speed is limited by the high mass, and the adjustment of the side pressing bars with respect to inner book thickness and to the projecting portion of the spine in general is complicated. In the first-mentioned arrangement, adjustment of the opening width is not provided and the adjustment of the telescopic side pressing bar in relation to the inner book thickness is possible only from outside, and is realised by a complex and expensive transmission of the rotary adjusting movement via universally jointed shafts. Because of the parallel crank arrangement the side pressing bars have only a short time to act on the inner book. The arrangement makes possible high cycling speeds.
It is the object of the present invention to provide a device for applying and pressing on a cover, having simple construction and comprising side pressing bars which open to a limited degree during the full reciprocating motion and can be set to a specific opening width during the upward movement of the back pressing plate.
The inventive concept lies in using connecting rods pivoted outside the carrier plate to actuate the side pressing bars, which connecting rods move the side pressing bars towards and away from the inner book during the reciprocating motion of the carrier plate and the back pressing plate, the outwardly-located pivot points being guided displaceably along the feed direction of the inner book conveyor. Essentially, the pivot points are entrained with the reciprocating movement over a partial section of its travel. The circular movement path of the side pressing bars, especially at the beginning and end, is thereby changed in such a way that the side pressing bars are not moved too far from the inner book and require only a limited range of movement. At the same time the side pressing bars are able to apply pressure for a longer period. The moving mass of the reciprocating pressing elements is kept low.
The outwardly-located pivot points are advantageously not arranged on the elements of the device which execute the vertical motion. The moving mass of the pressing elements is thereby further reduced.
Further advantages of the device according to the invention are the adjustments of the side pressing bars in relation to the inner book thickness and in relation to the projecting spine portion on the fixed-format side, which can be carried out from outside in a simple manner even while the machine is running, and the adjustment of the opening width during the upward movement of the back pressing plate. The device is suited to the manufacture of brochures having reinforcing strips and of lay-flat brochures.